The work supported by this grant is designed to elucidate structural parameters of steroids and other isopentenoids which govern the mechanism of biosynthetic reactions. Special attention is being given to the sterol side chain and the detail of metabolism at C-24. BIBLIOGRAPHIC REFERENCES: Nes, W.R., Alcaide, A., Mallory, F.B., Landrey, J.R., and Conner, R.L., "Dealkylation of 24-Ethylsterols by Tetrahymena pyriformis", Lipids, 10, 140 (1975). Nes, W.R., Krevitz, K., Behzadan, S., Patterson, G.W., Landrey, J.R., and Conner, R.L., "The Configuration of delta 5,7,22-Sterols in a Tracheophyte", Biochem. and Biophys. Res. Com., 66, 1462 (1975).